Suction line regulation

[scorpx]

Hi all

There is a system have 3 x screw Parallel compressors and 3 cold rooms
Refrigrant is R404A

all rooms temperatures sets are -22 C
I want to set one room 0C others -22C

How can I regulate the suction line for 0C room ?

Thanks...

[Rob White]

.

There is a regulator that is fitted directly after the
evaporator that is designed to do exactly that.

It is an EPR Evaporator Pressure Regulator and it needs
to be installed and set up to the correct pressure.

When set correct it will keep the evaporator at a higher
pressure which will keep the temperature higher.

404a You say, so 404a at room temp of -22degC will evaporate at about -32degC
if you want the room at 0degC then you will control the pressure so the evap temp
is about -10degC.

The suction pressure at -30 will be about 1barg so you will need to up the evaporator
pressure on the 0degC system to about 3.5barg and that is what the EPR does.

Regards

Rob

.

[Brian_UK]

Some Sporlan documentation on EPRs
http://www.sporlanonline.com/90-20.htm

[scorpx]

thanks for quick and good reply

[Sandro Baptista]

Hi all

There is a system have 3 x screw Parallel compressors and 3 cold rooms
Refrigrant is R404A

all rooms temperatures sets are -22 C
I want to set one room 0C others -22C

How can I regulate the suction line for 0C room ?

Thanks...

You can use as KVP or a ICS + CVP pilot depending on the capacity.

The pressure set should be made according with the DT1 considered to the evaporator. If the CVP is set to a lower pressure it can happen that when cold store 0ºC is working the compressors couldn't have sufficient capacity to handle the rest of the services and higher temperature fluctuation could occur.

[Sandro Baptista]

KVP and ICS are Danfoss automatic valves.

[scorpx]

What about Expansion valves.
I think If I use Electronic exp valves there will be no problem both -18 and -22C

?

[Rob White]

What about Expansion valves.
I think If I use Electronic exp valves there will be no problem both -18 and -22C

?

You do not have to change anything.

All you need to do is set the temperature control to the new higher temp,
but and there is a big BUT. But if you run the evap at -30degC you will have
a hugh temperature differance over the coil and that will cause problems.

If your going to do it do correctly and then it is done right.

Regards

Rob

.

[Sandro Baptista]

You do not have to change anything.

All you need to do is set the temperature control to the new higher temp,
but and there is a big BUT. But if you run the evap at -30degC you will have
a hugh temperature differance over the coil and that will cause problems.

If your going to do it do correctly and then it is done right.

Regards

Rob

.


I agree with Rob. A big difference will cause a huge ice formation on the evaporator, lost of humidity on the air and other problems.

[scorpx]

I must regulate the suction line because there is a big differance between two different room. -30 C evaporation in 0C room harmfull for product.

Best solution that I found is danfoss PM3 with 1 evm
this is the picture
9061
what you think ?

[Sandro Baptista]

Yes. But you just can use a PM1+CVP instead of a PM3+CVP+EVM. Do you really need to close the line (the purpose of the EVM pilot). A PM1 (for just one pilote) is cheaper.

In the future the PMs will not exist...the ICS valve (also from DANFOSS) appeared at the market maybe about 5 years ago and will replace the all PM series. You already can find the ICS up to DN150. At one year ago just up to DN65.

[Sandro Baptista]

Do you really need to close the line (the purpose of the EVM pilot)?

[Rob White]

.

You need a ORIT (SORIT) Valve.

See Sporlan product (but any equivalent valve will do).

http://www.carlyleccrp.com/site/catalog07/SPORLAN/SPORLAN-008.pdf

Regards

Rob

.

[Camille]

Hi

Room at -22C , 10C temperature difference between the room air and the evaporator coil temperature , your evaporative temperature will be -22C-(10C)= -32C E.T. [evaporative temperature], say 3 C degree line losses to compressors, your compressors will operate at -35C S.T. [suction tmeperature]

Room at 0C , 10C temperature difference between the room air and the evaporator temperature , your evaporative temperature will be 0C-(10C)= -10 C E.T.,

To maintain -10C at this evaporator and 0C for the room and not to pull to the minus 35C the compressors suction are operating at you will need an inlet pressure suction regulator on this evaporator or evaporators , that will create resistance or addtional pressure drop maintained by the suction valve port, this will create a hp penalty on your pump if it is a liquid recirculation system, or compressor penalty, the difference between the -32C E.T. [-22C room] and the -10C E.T. [0C room] is your saturated pressure penalty imposed

you will need a suction pressure inlet regulator valve , see Hansen web pages for an A4A regulator
www.hantech.com/


best of luck

Camille Zabbal